This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my applications entitled BUBBLE-JET TYPE INK-JET PRINT HEAD filed with the Korean Industrial Property Office on Jul. 11, 2000 and there duly assigned Serial No. 2000-39554 and entitled BUBBLE-JET TYPE INK-JET PRINT HEAD filed with the Korean Industrial Property Office on Nov. 9, 2000 and there duly assigned Serial No. 2000-66430.
1. Field of the Invention
The present invention relates to an ink-jet printhead, and more particularly, to a bubble-jet type ink-jet printhead.
2. Description of the Related Art
The ink ejection mechanisms of an ink-jet printer are largely categorized into two types: an electro-thermal transducer type (bubble-jet type) in which a heat source is employed to form a bubble in ink causing ink droplets to be ejected, and an electromechanical transducer type in which a piezoelectric crystal bends to change the volume of ink causing ink droplets to be expelled.
An ink-jet printhead having a bubble-jet type ink ejector needs to meet the following conditions. First, a simplified manufacturing procedure, low manufacturing cost, and high volume production must be allowed. Second, to produce high quality color images, creation of minute satellite droplets that trail ejected main droplets must be prevented. Third, when ink is ejected from one nozzle or ink refills an ink chamber after ink ejection, cross-talk with adjacent nozzles from which no ink is ejected must be prevented. Fourth, for a high speed print, a cycle beginning with ink ejection and ending with ink refill must be as short as possible. Fifth, a nozzle and an ink channel for introducing ink into the nozzle must not be clogged by foreign materials or solidified ink.
However, the above conditions tend to conflict with one another, and furthermore, the performance of an ink-jet printhead is closely associated with structures of an ink chamber, an ink channel, and a heater, the type of formation and expansion of bubbles, and the relative size of each component. Thus, due to the complicated structures of ink-jet printheads, the fabrication process is very complex and the manufacturing cost is very high. Furthermore, each ink channel having a complicated structure has a different fluid resistance to ink supplied to each chamber, which results in large differences in the amount of ink supplied to each chamber. Thus, this raises design concerns for adjusting the difference. Due to the complicated structures of the ink channel and ink chamber connected thereto, foreign materials may adhere to the ink channel and ink chamber or ink may solidify, which may not only cause an obstacle to supplying ink to the ink chamber but may also clog the ink channel or the nozzle rendering it unusable.
Meanwhile, an ink-jet printhead disclosed in U.S. Pat. No. 4,847,630 is constructed such that an annular heater surrounding each nozzle, from which ink is ejected, is formed in a nozzle plate, and a C-shaped isolation wall, one side of which is open, is disposed in the vicinity of the heater. The ink-jet print head printhead constructed such that the heater and the isolation wall are formed in the same nozzle plate is advantageous in reducing offset between the nozzle and the heater. However, heat loss due to the nozzle plate is large and the structure is complicated since the ink chamber formed by the isolation wall is provided for each nozzle.
To solve the above problems, it is an objective of the present invention to provide a bubble-jet type ink-jet printhead having a simplified structure which is simple to manufacture.
It is another objective of the present invention to provide a bubble-jet type ink-jet printhead which is capable of effectively preventing adhesion of foreign materials and ink solidification.
It is still another objective of the present invention to provide a bubble-jet type ink-jet printhead which has a low manufacturing cost and a long lifetime.
It is still another objective of the invention to provide a bubble-jet type ink-jet printhead having a self-cleaning function.
It is further an object of the present invention to provide a bubble-jet type ink-jet printhead which has little or no crosstalk between the nozzles.
It is also an object of the present invention to provide a bubble-jet type ink-jet printhead that can eject a droplet of ink without ejecting satellite droplets.
Accordingly, to achieve the above objectives, the present invention provides a bubble-jet type ink jet printhead which includes a substrate, a nozzle plate including a plurality of nozzles, which is separated a predetermined space from the substrate, walls for closing the space between the substrate and the nozzle plate and then forming a common chamber between the substrate and the nozzle plate, a plurality of resistive layers, formed on the substrate within the common chamber corresponding to the plurality of nozzles, each resistive layer encircling the central axis passing through the center of each nozzle, a plurality of pairs of wiring layers formed on the substrate, each pair of wiring layers being connecting to each resistive layer and extending to the outside of the common chamber, and a plurality of pads which are disposed at the outside of the common chamber on the substrate and electrically connected to the wiring layers.
Preferably, the plurality of resistive layers and the plurality of nozzles corresponding thereto are formed in two or more rows on the substrate and the nozzle plate, respectively. Preferably, a dam for dividing the common chamber into a plurality of regions and allowing ink to flow from one region to another by spatially connecting the plurality of regions is disposed within the common chamber, wherein the dam has a height smaller than the distance between the substrate and the nozzle plate. Furthermore, the dam is of a stack-type, which is stacked on the substrate, and/or of a rib-type dam which projects inwardly toward the substrate from the nozzle plate. Preferably, the resistive layer is formed in a doughnut-shape, one side of which is open, or an omega shape. A damping hole adjacent to each of the plurality of nozzles is formed in the nozzle plate, and in particular, the damping hole is formed between adjacent nozzles. Furthermore, preferably, one or more common chambers are arranged between the substrate and the nozzle plate, each common chamber being spatially isolated, and ink feed grooves are formed at two opposite ends of the substrate for supplying ink to both sides of the common chamber.
The present invention also provides a bubble-jet type ink-jet printhead which includes a substrate, a nozzle plate including a plurality of nozzles, which is separated a predetermined space from the substrate, walls for closing the space between the substrate and the nozzle plate and then forming a common chamber between the substrate and the nozzle plate, concave portions formed on the substrate corresponding to the nozzles, a plurality of resistive layers formed in the concave portions of the substrate within the common chamber corresponding to the plurality of nozzles, each resistive layer encircling the central axis passing through the center of each nozzle, a plurality of pairs of wiring layers formed on the substrate, each pair of wiring layers being connecting to each resistive layer and extending to the outside of the common chamber; and a plurality of pads which are disposed at the outside of the common chamber on is the substrate and electrically connected to the wiring layers.
Preferably, in the ink-jet printhead, a thermal insulating layer is formed on the substrate and the resistive layer is formed on the thermal insulating layer. A protective layer for protecting the resistive layer from ink within the common chamber is formed on the resistive layer. Furthermore, the diameter of the lower portion of the nozzle that faces the common chamber is greater than or equal to the diameter of the concave portion, on which the resistive layer is formed, and it is greater than the distance between the distance between the substrate and the nozzle plate.